Sanghee Kim

Enantioselective syntheses of (+)-decursinol and (+)-trans-decursidinol

Abstract Selective and practical asymmetric syntheses of (+)-decursinol ( 1 ) and (+)- trans -decursidinol ( 2 ) have been achieved using naturally occurring umbelliferone, demethylsuberosin, and xanthyletin as the synthetic intermediates. The absolute stereochemistry was established in the late stage of synthesis by employing Jacobsens enantioselective epoxidation conditions.

Total synthesis and determination of the absolute configuration of (+)-neoisoprelaurefucin

The first total synthesis of the seven-membered ring ether marine natural product (+)-neoisoprelaurefucin (1) has been achieved employing a regioselective internal alkylation of amide 3, a novel sequence for removal of the triethylsilyl group from the resulting triethylsilyloxepene 2, and a bromoetherification of alcohol 16 as key steps. In addition, the absolute stereochemistry of the natural product was assigned.

Efficient construction of bicyclic systems by an internal SN2′ enolate alkylation/ring-closing metathesis (RCM) strategy: a concise synthesis of the trans-hydrindane nucleus

Abstract A concise and efficient synthesis of the trans-hydrindane system has been achieved by a novel intramolecular SN2′ enolate alkylation/ring-closing metathesis (RCM) strategy with a good degree of stereocontrol.

Stereoselective synthesis of amino-substituted apio dideoxynucleosides through a distant neighboring group effect

Abstract Novel amino-substituted apio nucleoside (2R,4R)-LJ-45 as a potential anti-HBV agent was stereoselectively synthesized from the known oxazolidine 1 through a distant neighboring group effect. It is believed that this synthetic method using a chiral template, (−)- l -serine methyl ester can be generally applied to the synthesis of other chiral amino-substituted nucleosides.

Influence of Impurities in SiC Powder on High Quality SiC Crystal Growth

SiC powders having different purities were prepared by carbothermal reduction under different conditions from traditional process and SiC single crystals were grown by the PVT method from the powders. After crystal growth, boule was cut to wafers and they were polished for chemical and defect analyses. Total impurities including Al, B and Ti which were derived from powders decreased remarkably during crystal growth. The formation of defects including micropipe and dislocations such as TED, TSD and BPD was strongly influenced by impurity content. The effect of impurity seemed to be negligible at below 1ppm level for MPD. On the other hand, dislocations continuously decreased even more when higher purity SiC powder below 1ppm level was used.